Actually close olds blocks in reloadBlocks

This fixes a bug leaking memory because blocks were not actually closed
as the closing call references the initial, empty slice

db.go

@@ -366,7 +366,7 @@ func (db *DB) seqBlock(i int) (Block, bool) {
 
 func (db *DB) reloadBlocks() error {
 	var cs []io.Closer
-	defer closeAll(cs...)
+	defer func() { closeAll(cs...) }()
 
 	db.mtx.Lock()
 	defer db.mtx.Unlock()
@@ -423,7 +423,7 @@ func (db *DB) reloadBlocks() error {
 	// Close all blocks that we no longer need. They are closed after returning all
 	// locks to avoid questionable locking order.
 	for _, b := range db.blocks {
-		if nb := seqBlocks[b.Meta().Sequence]; nb != b {
+		if nb, ok := seqBlocks[b.Meta().Sequence]; !ok || nb != b {
 			cs = append(cs, b)
 		}
 	}

head.go

@@ -53,8 +53,7 @@ type headBlock struct {
 	values   map[string]stringset // label names to possible values
 	postings *memPostings         // postings lists for terms
 
-	metamtx sync.RWMutex
-	meta    BlockMeta
+	meta BlockMeta
 }
 
 func createHeadBlock(dir string, seq int, l log.Logger, mint, maxt int64) (*headBlock, error) {
@@ -109,6 +108,7 @@ func openHeadBlock(dir string, l log.Logger) (*headBlock, error) {
 
 	r := wal.Reader()
 
+Outer:
 	for r.Next() {
 		series, samples := r.At()
 
@@ -117,6 +117,10 @@ func openHeadBlock(dir string, l log.Logger) (*headBlock, error) {
 			h.meta.Stats.NumSeries++
 		}
 		for _, s := range samples {
+			if int(s.ref) >= len(h.series) {
+				l.Log("msg", "unknown series reference, abort WAL restore", "got", s.ref, "max", len(h.series)-1)
+				break Outer
+			}
 			h.series[s.ref].append(s.t, s.v)
 
 			if !h.inBounds(s.t) {
@@ -168,10 +172,19 @@ func (h *headBlock) Close() error {
 }
 
 func (h *headBlock) Meta() BlockMeta {
-	h.metamtx.RLock()
-	defer h.metamtx.RUnlock()
+	m := BlockMeta{
+		ULID:       h.meta.ULID,
+		Sequence:   h.meta.Sequence,
+		MinTime:    h.meta.MinTime,
+		MaxTime:    h.meta.MaxTime,
+		Compaction: h.meta.Compaction,
+	}
 
-	return h.meta
+	m.Stats.NumChunks = atomic.LoadUint64(&h.meta.Stats.NumChunks)
+	m.Stats.NumSeries = atomic.LoadUint64(&h.meta.Stats.NumSeries)
+	m.Stats.NumSamples = atomic.LoadUint64(&h.meta.Stats.NumSamples)
+
+	return m
 }
 
 func (h *headBlock) Dir() string         { return h.dir }
@@ -199,6 +212,11 @@ func (h *headBlock) Querier(mint, maxt int64) Querier {
 			ep := make([]uint32, 0, 64)
 
 			for p.Next() {
+				// Skip posting entries that include series added after we
+				// instantiated the querier.
+				if int(p.At()) >= len(series) {
+					break
+				}
 				ep = append(ep, p.At())
 			}
 			if err := p.Err(); err != nil {
@@ -413,11 +431,8 @@ func (a *headAppender) Commit() error {
 
 	a.mtx.RUnlock()
 
-	a.metamtx.Lock()
-	defer a.metamtx.Unlock()
-
-	a.meta.Stats.NumSamples += total
-	a.meta.Stats.NumSeries += uint64(len(a.newSeries))
+	atomic.AddUint64(&a.meta.Stats.NumSamples, total)
+	atomic.AddUint64(&a.meta.Stats.NumSeries, uint64(len(a.newSeries)))
 
 	return nil
 }